Florfenicol is a kind of chloramphenicol extensive antibacterial, formed chemically. The representative florfenicol wastewater is a sort of high strength organic industrial wastewater, containing high concentration of organics, salts, heavy metals, sulfate and ammonia. Similar industrial wastewaters are produced from the formation of: monosodium glutamate, lysine, molasses, midecamycin, terramycin and fatty acid, in which the BOD5 concentration is several million mg/L, TKN several thousand mg/L and sulfate several thousand mg/L.
One representative process of florfenicol formation is:
Where (a) NaSO3, NaHCO3; (b) CH3SO3Na; (c) Br2; (d) NH2CH2COOH, CuSO4, NHOH; (e) EtOH, H2SO4; (f) Tartaric acid dissociation; (g) NaBH4; (h) Dichloroacetonitrile, vitriol, ammonia saturated 2-propanol, 80° C., 2 h ; (i) FPA, THF, 100° C., 2 h; (j) Potassium acetic acid, methanol, 2-propanol , water, 10 h , pH 3.5-4.0.
In the process of florfenicol formation: (a-d) is indented to the section of copper-ion-containing wastewater comprising high concentration of copper ion, ammonia complex compound and sulfate; (e) is the wastewater of esterification section; (f-h) is the wastewater of dissociation section; (i-j) is the wastewater of florfenicol formation section.
For this kind of organic wastewater, using simple treatment method cannot the effluent discharge standards, so combining several treatment technologies is necessary. Four methods for treating industrial wastewater are: physical methods, chemical methods, physiochemical methods and biological methods. The last one is the most economical and efficient. Aerobic biological treatment is a popular technology for treating low strength organic wastewater, but for refractory organic wastewater, advanced chemical, physiochemical or biological pretreatment are needed to change the molecular structure of refractory material, reduce the concentration of pollutants, decrease the toxicity and increase the ratio of BOD5 to COD. After pretreatment, the wastewater becomes more decomposable, stable and high efficient performance could be achieved. Anaerobic biological process is usually used for treating high strength refractory organic wastewater. Yet, the presence of high concentrations of copper ion, sulfate and ammonia in florfenicol wastewater negatively affects the growth of anaerobic bacteria.
Main methods reported for treating high strength copper ion wastewater comprise: alkali neutralization, sulfide sodium sedimentation, iron slag replacement, extraction, electrolysis, membrane separation, resin or activated carbon adsorption, ion exchange, reverse osmosis, electrodialysis, evaporation condensation, biological treatment and so on. Physiochemical methods (such as ion exchange) need expensive investment and operation cost, while chemical methods such as neutralization and sedimentation are economical. Chemical sedimentation and biological methods have been reported to be the main technologies for treating copper-ion-containing pharmaceutical organic wastewater: adding Na2S to remove copper salt, adjusting pH by alkaline material, and then using hydrolysis and fermentation and aerobic treatment. Yet, high sulfate and ammonia concentration cannot be solved in this method and another problem is the remaining S2− in the solution will inhibit the activity of anaerobic bacteria after sedimentation reaction.
Main methods reported for treating high sulfate and organic concentration wastewater comprise: tail gas scrubbing and recycle mono-phase anaerobic process to reduce hydrogen sulfide toxicity; two phase anaerobic process for reducing hydrogen sulfide toxicity; ion salt sedimentation and/or inhibitors to control hydrogen sulfide toxicity to methanobacteria; photosynthetic bacteria treatment process. To treat the chloramphenicol-production wastewater, scarcely can these methods meet the effluent discharge standards.